Construction of earphones and microphones



Oct. 11, 1966 J. c. CRAIG ET AL 3,278,695

CONSTRUCTION OF EARPHONES AND MICROPHONES Filed March 21, 1963 INVENTORS JAMES C. CRAIG ALEXANDER L. DVORSKY AT TORNEY United States Patent 3,278,695 CONSTRUCTION OF EARPHONES AND MICROPHONES James C. Craig and Alexander L. Dvorsky, Conneaut,

Ohio, assignors to The Astatic Corporation, Conneaut,

Ohio, a corporation of Ohio Filed Mar. 21, 1963, Ser. No. 266,968 Claims. (Cl. 179-110) This invention relates to the construction of earphones, microphones and the like, and more particularly to improved means for securing the electro-mechanical transducer elements within such devices.

In the construction of earphones and microphones,

it is essential to provide an edge-supported diaphragm for vibratory motion in air, a mechanical connection from a vibratile portion for said diaphragm to a transducer which is capable of converting electrical currents into mechanical motion or vice versa, and suitable mounting means for said transducer. The present invention provides improved means for performing the latter function especially.

In US. Patent No. 2,931,865 to A. L. Dvorsky and in US. Patent No. 3,007,013 to C. F. Paull et al, there are disclosed and claimed certain preferred constructions for the supporting and securing of transducer elements in microphones. The present invention seeks to provide new and improved means for achieving the same functions in the construction of microphones and further discloses transducer mounting means of particular utility in the building of earphones. It is to be noted that most of the same parameters which govern the design of microphones apply equally to the design of earphones, the prime difference being in the direction of transduction. Whereas, in a microphone the diaphragm is subjected to pressure Waves in air and the transducer linked to the diaphragm converts these to fluctuating electrical signals, in earphones the converse is true. i.e. electrical signals are applied to the transducer member which deforms physically and causesmotion of its associated diaphragm so that acoustical waves are set up in space surrounding the diaphragm. In the case of the earphones of the present invention these acoustical waves are impressed upon the eardrums of the user to convey audible signals.

In the earphone construction of the present invention there is provided a novel and highly efficient means for mounting a transducer element. The accessory parts used to mount the transducer are but three in number and they are duplicate parts stamped from sheet plastic material in a highly economical manner. The mounting parts being of selected hardness, exhibit highly desirable elastic restraint to the transducer member to achieve a further object of the invention. The relative thinness of the mounting parts allows substantially unimpeded freedom for the transducer to flex and thus achieves increased efliciency which is a further object of the invention.

A still further object is the provision of novel means to secure electrical connection to the electrodes of the transducer and the mounting parts assist in this also.

These and other objects and advantages of the invention will become apparent upon consideration of the following specification and the accompanying drawing wherein there is disclosed a preferred embodiment of the invention.

3,278,695 Patented Oct. 11, 1966 In the drawing:

FIGURE 1 is a sectional view thru the earphone or the like of the present invention, this view being taken along the line I-I of FIGURE 2;

FIGURE 2 is a plan view, partly in section, of the earphone of FIGURE 1 and taken along the line IIII of FIGURE 1;

FIGURE 3 is a side elevation of the transducer element and its mounting means as used in FIGURES 1 and 2; and

FIGURE 4 is a view, partly in section taken along the line IV-IV of FIGURE 3.

Referring now to the drawing in detail, and particularly to FIGURES 1 and 2, reference numeral 10 indicates a back housing of the earphone, made preferably of molded plastic material, and comprising a cup-like portion 11 and a flaring flange-like upper skirt 12. In a raised position within cup-like portion 11 a flat-faced platform 13 is provided. Under platform 13 a cavity 14 is provided and it is closed off from the cup-like portion 11 by a vertically disposed wall 15. Extending through wall 15 and secured therein is a pair of terminal pins 16. The inner ends 16 of these pins extend into cup portion 11 and the outer ends 16" thereof extend into cavity 14 where they may be attached to electrical leads, not shown.

On the inner face of upper skirt 12 a flat ledge 17 is provided to support the edge of a thin formed diaphragm 18. A gasket 19 overlies the supported edge of diaphragm '18 and both gasket 19 and diaphragm 18 are located centrally of back housing 10 by an upstanding rim 20 formed integrally with skirt 1-2. At the extreme upper edge of skirt 12 a second upstanding rim 21 is provided.

A contoured face plate 22 is assembled against the skirt 12 and plate 22 is formed with a shoulder 23 and a groove 24 to mate with rims 20 and 21, respectively, and to hold plate 22 centrally located with respect to skirt 12. The lower face of shoulder 23 bears on gasket 19 and holds it and the edge of diaphragm 18 securely clamped. A suitable adhesive, for example, may be applied in the space between rim 21 and groove 24 to keep the face plate 22 and skirt 12 together.

The outer surface of face plate 22 is suitably contoured to fit against the ear of the user in a comfortable manner. At the center of face plate 22 a plurality of holes 25 afford an acoustical path from the face of diaphragm 18 to the outer surface of face plate 22. A disk of cloth or other foraminous material 26 may be applied over the inner ends of holes 25, if desired, to modify the acoustical character of the assembly and/or to exclude dust.

The diaphragm 18 has an annular groove 27 formed about its outer edge. Groove 27 defines an area of flexibility by virtue of which the center conical portion 28 of the diaphragm 18 may move upwardly and downwardly as a substantially rigid piston, in well known manner. The apex of the conical portion 28 affords an ideal point at which to attach the diaphragm 18 to a drive member 30.

In mounting the transducer element in accordance with the present invention use is made of the substantially flat area afforded by the top surface of platform 13. Transducer element 40 is illustrated, in FIGURES 2 and 3 especially, as being of the ceramic bimorph type. Element 40 comprises an upper slab 4'1 and a lower slab 42 of polarized piezoelectric ceramic material such as lead zirconia titanate, for example, adhered to a center conductive electrode 43. Outer conductive electrode areas occur also on the two outer major faces of the slabs 41 and 42. The entire element 40 is adapted by its structure and by its induced electrical properties to be applied as a beam supported at both ends.

To support the element 40 in a manner to achieve the objects of the present invention, the opposite ends thereof are held in novel support members 50. Each support member 50 comprises a single-piece stamping punched from a sheet of medium hard polymeric plastic, such as polypropylene, for example. The two support members 50 and the drive member 30, referred to above, preferably are identical in structure to achieve the economies envisaged. The support members 50 and the drive member 30 consist of a large rectangular frame portion 51 adapted to securely encircle element 40 and an outwardly protruding stem 52 made integral therewith.

In assembling the various parts of the earphone of the present invention, the drive member 30 is first slipped over the middle of element 40 with its stem 52 disposed upwardly. The support member 50 at the left end of element 40, as viewed in FIGURE 3, is next slipped over the element 40 with its stem 52 protruding downwardly. A foil lead 55 is now attached to the center electrode 43 by soldering for example. A second foil lead 56 is folded over the right end of element 40, as viewed in FIGURE 3, and the right support member 50 is slipped over both the foil lead 56 and the right end of element 40. Lead 56 is freedup slightly to provide a free-standing foil loop 57, which affords clearance between the center of loop 57 and the end of electrode 43, as shown. Support member 50, by its resilience, presses the captured portions of lead 56 into firm contact with the upper electrode of ceramic slab 41 and the lower electrode of slab 42 of element 40 to establish electrical connection therewith.

On the flat-faced platform 16 within cup 11, a pair of spaced holes 60 are provided to accommodate the downwardly extending stems 52 of support members 50. Stems 52 are secured in holes 60 by pressfitting, together with the use of a suitable cement 61, if required, and the element 40 is thus secured above the platform 13, spaced therefrom, and lying parallel therewith. The foil leads 55 and 56 are next secured in electrical contact to the respective ones of the inner ends 16 of terminal pins 16 by soldering, for example. The drive member 30 has its stem 52 extending up toward the apex 28 of diaphragm 18 where it is received in an aperture and is secured by adhesive 62. The placing of gasket 19 and face plate 22 over the diaphragm 1 8 and the adhering of plate 22 to skirt 12 completes the closing up of the assembled earphone of the present invention.

In addition to the novel features above disclosed for practicing the present invention, there are also provided in the presently disclosed earphone means for advantageously practicing the invention of the above identified Dvorsky US. patent. In the cup-like molding 11 of FIG- URE 2, there are provided mounting ribs 70, locating pins 71 and contact supporting bosses 72 which are to be utilized in mounting a Rochelle Salt transducer element in the present earphone, in a manner taught by the Dvorsky patent. While the present disclosure shows a bimorph transducer element 40, having two layers of ceramic material 41 and 42, and a metal electrode 43 in its structure, it is contemplated that other and improved types of transducer elements may be used to advantage in the assembly of the earphone disclosed herein. For example, a four-layer transducer of the kind disclosed in co-pending application for US. Patent Serial No. 256,707 filed on February 6, 196-3 and assigned to the assignee of the present invention, will be understood to find advantageous application in the instant device.

Thus, there has been disclosed a preferred assembly of novel parts which accomplishes the objects initially set forth. The mounting members 50, to be used in securing the element 40 in operative position and for connecting it to the diaphragm 18, are simple and extremely cheap to fabricate. They are easily and quickly assembled to the element 40 and, when assembled in the manner contemplated, support the element 40 with an optimum degree of mechanical compliance. The relative thinness of the support members 50 afford substantially knifeedge support for element 40 and permit an extensive free portion of the same to operate with utmost efficiency in driving diaphragm 18. The resilient character of the plastic material, from which mounting members 50 are fabricated, afford clamping for suppression of resonances in the earphone unit of the invention. The inherent resilience of the mounting members 50 is used to assure secure electrical contact to the electrode areas of transducer element 40.

Application of the'principles of our invention makes possible the commercial production of high quality sound reproduction components at extremely low cost. While we have disclosed specifically an earphone, it should be quite obvious that substantially the same construction is ideally suited for microphones and similar devices necessitatingonly variations in the shape and dimension of the principal housing sections, corresponding to members 10 and 22 of FIGURE 1. It should be noted particularly that the well portion of section 10 together with the diaphragm 28 provides a fluid-tight enclosure for the piezoelectric transducer employed as well as a housing for the electrical leads. Further economies are affected by utilizing the inherent material of the section 10 itself to support the transducer, thereby dispensing with any need for further housing or support members.

Having thus described our invention, we claim:

1. Structure for earphones, microphones, and the like, comprising a casing having an open side, a flat surface in said casing facing said open side, a pair of spaced bores in said flat surface, a bar-like piezoelectric transducer overlying said surface but spaced therefrom, a transducer supporting member secured in each of said bores, said transducer supporting members each comprising a frame adapted to surround said bar-like transducer and a stem adapted to be secured in one of said bores, a diaphragm secured to the open side of said casing and a mechanical connection joining said diaphragm and said transducer.

2. Structure for earphones, microphones, and the like, comprising a casing, a plurality of spaced supporting .frames secured in spaced bores in a wall of said casing and extending vertically from said well of said casing, a piezoelectric transducer element disposed in said frames and bridging the space therebetween, the resilience of said frames securing said transducer, a diaphragm, a drive member secured to said transducer between said frames and connecting said transducer and diaphragm.

'3. A formed plastic elastomer member for supporting a bar-like piezoelectric transducer element of an earphone or a microphone in the internal cavity of the housing thereof/and for coupling said element to an acoustic diaphragm, said member having a rectangular frame portion adapted to encompass and elastically secure itself around said element and having an integral stern protruding outwardly of a side of said frame, said stern being adapted to be secured to said casing or to said diaphragm.

4. Structure for an earphone, microphone or the like, which comprises an open-sided casing having a flat interior supporting surface, spaced bores in said surface, a diaphragm supported over the open side of said casing, an aperture in said diaphragm, a transducer element encircled by three separate frame-like elastomeric members each having a radially extending stem portion thereon, two of said stem portions adhered in said spaced bores and one of said stem portions adhered in said aperture in said diaphragm.

5. Structure for earphones, microphones, and the like,

comprising a casing, a bar-like piezoelectric transducer having an electrode area on one of its outer surfaces, a

resilient insulating member supported by and secured within said casing and having a window for the tight reception of a portion of said transducer, and a flexible metal foil electrical conductor constituting a connector for said transducer, said conductor being clamped in said window in tight contact with said electrode area, said transducer being of the bimorph type and having a centrally disposed electrode and electrode areas on opposite side faces of the transducer, and said flexible conductor being looped over an end of said transducer and tightly received in said window in pressure contact with both said electrode areas.

References Cited by the Examiner UNITED STATES PATENTS 2,506,608 5/1950 McLoad 34010 2,933,628 4/ 1960 Samuelson 3109.1 3,007,013 10/1961 Pau1le't al 179l21 KATHLEEN H. CLAFFY, Primary Examiner.

10 ROBERT H. ROSE, Examiner.

F. N. CART-EN, Assistant Examiner. 

2. STRUCTURE FOR EARPHONES, MICROPHONES, AND THE LIKE, COMPRISING A CASING, A PLURALITY OF SPACED SUPPROTING FRAMES SECURED IN SPACED BORES INA WALL OF SAID CASING, A AND EXTENDING VERTICALLY FROM SAID WALL OF SAID CASING, A PIEZOELECTRIC TRANSDUCER ELEMENT DISPOSED IN SAID FRAMES AND BRIDGING THE SPACE THEREBETWEEN, THE RESILIENCE OF SAID FRAMES SECURING SAID TRANSDUCER, A DIAPHRAGM, A DRIVE MEMBER SECURED TO SAID TRANSDUCER BETWEEN SAID FRAMES AND CONNECTING SAID TRANSDUCER AND DIAPHRAGM. 